For example, the ISO standard family 11898-1 through -5 describes the Controller Area Network (CAN) as well as an extension of the CAN designated as “time-triggered CAN” (TTCAN). The media access control method used in the CAN is based on a bit-wise arbitration. The user stations are simultaneously able to begin transmitting a message over the bus. The messages sent have an identification which is transmitted after a single “start of frame” bit. In the bit-wise arbitration, while sending the bits belonging to the identification, are simultaneously able to ascertain the logical state (0 or 1) of the bus. If the value of a bit sent by a first user station does not correspond to the ascertained logical state of the bus, another user station has obviously sent a message having a higher priority, and the first user station therefore ends its send access to the bus. The bit-wise arbitration thus achieves a non-destructive transmission of that message via the bus that wins the arbitration process.
With the increasing electronization of modern vehicles, and the advent of additional systems for the improvement of driving safety, for example, or driver convenience, the requirements with respect to the consumption of electric power are growing constantly. At the same time, the necessity exists of limiting the power usage, in order to take into account ecological and legal requirements. Even against the background of the increased introduction of electrically driven vehicles, it is indicated that power usage by control and regulating systems and safety and convenience systems should be kept within limits, since the electric power used has a direct effect on the vehicle's distance range.
For that reason, it is provided in new vehicles that one should put individual bus users or groups of bus users completely or partially at rest if the function exerted by them or the respective subfunctionality is not required. Along with that comes the requirement to wake up again or to activate bus users that are at rest, wholly or partially, when the function or the subfunctionality that is at rest is required again.
In this connection, German Patent Application DE 103 58 584 A1 discusses a device and a method for selectively waking up users of a bus system, in which a detecting arrangement, particularly a counter, is provided which detects at least one predefined signal property of the signals transmitted on the bus system and initiates the further wake-up procedure once a specifiable number has been reached.
Patent Application DE 102 25 578 A1 discusses a method and a device for the selective activation of bus users, which is distinguished by providing a separate voltage regulator for the protocol controller present in the bus user. Because of that, when bus communication takes place, the protocol controller may first be awakened without the associated application controller, the former then being available for comparing the messages present on the bus to one or more previously stored reference messages. If there is agreement, the application controller and with that, the entire bus user is awakened.
In the devices from the related art, after the waking process has taken place, the information as to by which signal or which message the waking process was triggered, is no longer present. This may be of disadvantage, particularly if different messages are supposed to lead to different properties of the awakened bus users. For example, if different waking messages for waking different subfunctionalities are to be drawn upon, the related art then does not supply satisfying results in every respect, since after the waking process has taken place, no information is available on the content of the message that has led to the waking up. If it were present, this information could be used to adjust the waking process depending on the reason for the waking, that is, depending on the requested functionality.